1. Field of the Invention
This invention relates to an angular member to be used for towing seismic cables, which are towed by a vessel in a position laterally displaced and in parallel relative to the course of travel of the vessel, with a frame member at least partly enclosing said cable in the area of angular deflection.
2. Description of the Prior Art
In seismic explorations at sea it may be desirable to provide a number of cables side-by-side in parallel behind the towing vessel, and this is especially done in connection with gun cables. Recently, explorations have also been made with several hydrophone cables or streamers side-by-side in parallel behind the towing vessel. For displacing the cables laterally, otter board devices and buoyancy means are conventionally used which are attached to a point on the cable. Thus, the inner portion of the cable will extend obliquely to the towing direction, and at the point where the buoyancy means and otter boards are secured, from which point cable extends in parallel with the towing direction, a very heavy load is produced. Not only is there a break or bending point in the cable, but yanking occurs due to the movement of the buoyancy means in the water, especially on the oblique inner portion. This can have a damaging effect on the attachment to the buoyancy means as well as on the cable itself that may break at this point. Furthermore, there is a special problem in connection with hydrophone cables or streamers which are provided with sensitive hydrophones and other electronic equipment which, indeed, can be disturbed by such yanking and wear and tear. Efforts have been made, previously, to eliminate these problems by providing a special towing cable running to said otter board/buoyancy means at the front edge of the main cable and by securing the latter to the towing cable at several points, but this system is very bothersome, especially when cables are hauled in or payed out, and above all, when there are a number of cables to be taken onto the same deck. Furthermore, efforts have been made to shape protecting means for the place of angular deflection, but such means caused much friction due to the high forces encountered, later resulting in fractures.